Numerous air cleaning or filtering mechanisms are known in the prior art. Broadly described, these air cleaning mechanisms function by interposing a porous medium within the air flow to separate particulate material therefrom. The porous medium has been configured as a hollow tubular filter element in a number of prior art devices. Cotton sateen with an internal wire mesh separater and pleated paper have been used in some prior art filtering devices as the porous media for the tubular filter elements. The filter elements remove the the particulate material from the air stream by allowing the particulate material to deposit on a surface of the tubular filter element. The collected particulate material must be periodically removed from the filter element.
A common technique for removing the collected particulate material from the filter elements is backwashing, or reverse jet pulsing. In this technique, a blast of pressurized fluid is sent through the filter element in a direction reverse to the direction of travel of the air being cleaned. The blast of pressurized fluid causes the collected particulate material to dislodge from the surface of the filter element.
The prior art filtering devices which utilize the backwashing technique to periodically clean filter elements use a mechanism discrete from the backwashing mechanism for causing the air flow through the filtering device. A backwashing mechanism of the prior art is typically comprised of separate conduits or piping and associated control valves. Filtering devices which use the backwash technique are disclosed in U.S. Pat. No. 3,729,903, issued to Espeel et al. on May 1, 1973; U.S. Pat. No. 3,798,878 issued to Pausch on Mar. 26, 1974; U.S. Pat. No. 4,077,781 issued to Sundstrom on Mar. 7, 1978; and British Pat. No. 1,516,721 issued to Donaldson Company, Inc. As will be seen more fully hereinafter, the present invention combines the backwash and air inducing functions into a single mechanism, thus simplifying the filtering device and allowing it to be more compactly constructed.